The present invention relates to a compensating element.
A thermal protection sleeve is described in German Published Patent Application No. 197 43 103, which encircles a fuel injector at a nozzle body. The thermal protection sleeve is inserted into a stepped receiving borehole of a cylinder head of an internal combustion engine, and circumferentially surrounds an ejection-side nozzle body segment of a fuel injector inserted into the receiving borehole. One end of the thermal protection sleeve has a collar, which rests against a step of the receiving borehole. In addition, the ejection-side end of the thermal protection sleeve has a folded section, which renders a certain length of the sleeve double-layered. In this region, the sleeve is radially locked between the nozzle body and the bore in the cylinder head. Since a tapered segment of the thermal protection sleeve, against which a correspondingly tapered segment of the fuel injector rests, is adjacent to the double-layered segment in the direction of the fuel supply line of the fuel injector, a certain transfer of axial force from the nozzle body of the fuel injector to the thermal protection sleeve is possible. However, this does not at all allow one to adjust the tolerances of the position of the fuel injector in the receiving borehole.
A fuel injection system having a compensating element is described in German Published Patent Application No. 197 35 665, the compensating element being made of a supporting body which has a dome-shaped supporting surface. A fuel injector is supported by this compensating element, in a receiving borehole of a cylinder head. Since the supporting surface of the fuel injector rests on the spherically shaped surface, the fuel injector can be mounted at an angle deviating from the axis of the receiving hole by up to a certain amount, and can be pressed firmly into the receiving borehole by a suitable device, e.g. a clamping shoe. This allows for a simple adaptation to the fuel supply lines. Thus, one can compensate for tolerances during manufacturing and mounting.
However, it is disadvantageous that the supporting body is expensive to manufacture and requires a precisely manufactured, spherical surface. In addition, it cannot be preassembled with the fuel injector during installation, and the two cannot be inserted as a unit.
The variant proposed in German Published Patent Application No. 197 35 665, of forming the spherical surface on the cylinder head itself and thus, obviating a separate component part, has the disadvantage that the spherical surface requiring a high degree of accuracy must be formed in a bore, at the relatively large workpiece for the entire cylinder head. Therefore, this has disadvantages from the standpoint of production engineering.
German Published Patent Application No. 197 35 665 also proposes an intermediate piece on the inlet side of a fuel injector, in order to compensate for tolerances with respect to the axes of the fuel injector and a fuel-outlet orifice of a fuel-intake manifold. In this context, a nozzle body of the fuel injector is inserted into a receiving borehole of a cylinder head, and is held by a suitable retaining device, e.g. a clamping shoe, which means that the position of the fuel-injector axis is preselected. A possible, axial offset between the axis of the fuel injector and the axis of the fuel-outlet orifice of the fuel-intake manifold is compensated for by tilting the intermediate piece disposed between the axes. In each case, this is sealed by a sealing ring in the direction of the fuel-intake manifold, as well as in the direction of the fuel injector.
It is disadvantageous to have the additional expenditure associated with having several more components, and to have the additional number of connections to be sealed. Since the intermediate piece requires an increased overall height, it can only be designed to be relatively short. This results in the need for the intermediate piece to already be at a relatively large angle to the axes, when the axial offset to be adjusted is small. However, in the case of bending, the sealing ring""s seal between the fuel injector and the intermediate piece, on one hand, and between the fuel-outlet orifice and the intermediate piece, on the other hand, is only based on the elasticity of the specific sealing ring. Therefore, there is the danger of the sealing rings not being uniformly compressed between the respective sealing surfaces, when the angle is too large. This can result in leakage.
In contrast, the compensating element of the present invention allows the fuel injector to be tilted with respect to the axis of the receiving borehole, over a relatively large angular range. In addition, the compensating element of the present invention is simple and inexpensive to manufacture. Furthermore, the compensating element transmits the axial force between the fuel injector and the receiving borehole in the cylinder head, the receiving borehole supporting the fuel injector in opposition to the retention force holding it in place. Therefore, the retention force and the position of the fuel injector can easily be adjusted, since the compensating element advantageously deflects in a flexible manner.
Therefore, the use of a compensating element designed according to the present invention allows for relatively large manufacturing tolerances in the manufacture of the cylinder head, as well as in the manufacture of the fuel injector and the fuel-intake manifold.
The compensating sleeve of the compensating element is advantageously in the form of a corrugated tube. This is easy to manufacture and allows both a large degree of longitudinal adjustment, and extensive tilting or bending along its longitudinal axis.
If the compensating element is supported at a conical step of the fuel injector, by an endface that is conical as well, then the axial retention force is consequently transmitted to the compensating element in an advantageous manner. In the case in which an angle exists between the axis of the fuel injector and the axis of the receiving borehole, the flexible segment is accordingly compressed on one side, until the conical end face makes uniform contact.
The compensating element advantageously has a sealing ring, which is situated between a step of the receiving borehole and a preformed shoulder of the support segment. Since the contact pressure of the seal is produced by the axial retaining force holding down the fuel injector and compensating element in the borehole, and not by radially squeezing a sealing ring in a borehole, the unit made of the fuel injector and compensating element can therefore be easily assembled and disassembled. The compression of the seal can be advantageously limited by a radial support ring, which surrounds the sealing ring on the outside.
The compensating element can be simplified in an advantageous manner, when a radially outward corrugation of the compensating sleeve, which in the form of a corrugated tube, is used as a preformed shoulder.
The service life of the compensating element can be increased in an advantageous manner, when a heat-resistant elastomer, Teflon(copyright), or graphite is used for the sealing ring, between the support segment and the receiving borehole.
A higher compressibility and bendability, especially of the flexible segment, can be attained using the same dimensions, when spring steel is used for manufacturing the compensating sleeve.
An advantageous design of the compensating element according to the present invention is achieved, when the diameter of the connecting segment is dimensioned to form an interference fit with the corresponding segment of the fuel injector, when small forces are applied. On one hand, the compensating element can still be slid easily onto the nozzle body, but on the other hand, it forms a preassembled unit with the fuel injector, without any special fastener, the unit already including all of the seals, as well. This simplifies the installation of the fuel injector.